Various patents disclose methods and apparatus for forming, molding, and filling a container. See, for example, U.S. Pat. Nos. 3,251,915, 3,464,085, 3,523,401, 3,597,793, 3,664,793, 3,674,405, 3,919,374, 4,176,153, 4,178,976, Re. 27,155 and patents cited therein.
Some of the methods and apparatus disclosed in the above-identified patents employ an extendable and retractable blowing and filling assembly having means operative on a length of extruded parison in a main mold for blow molding the container body portion through a top opening in the parison and for then filling the molded container with a liquid product through the top opening. Such a blowing and filling assembly typically includes an outer mandrel tube having a lower end portion defining an exterior mandrel surface adapted for engaging a portion of the interior surface of the length of parison to seal the parison opening with the exterior mandrel surface pressing the parison against the main mold. Typically, the blowing and filling assembly outer mandrel tube also defines an interior chamber in which is disposed an inner tube.
Various internal arrangements are disclosed in some of the above-identified patents for such assemblies whereby pressurized gas is discharged for blow molding the container, whereby the pressurized gas is vented from the container after it is blow molded, and whereby the liquid product is subsequently discharged into the container. The above-listed U.S. Pat. No. 3,597,793 discloses such an assembly wherein the liquid product is discharged through an inner tube into the container when a flat valve plate at the end of the inner tube is opened. U.S. Pat. No. 3,523,401, along with U.S. Pat. Nos. 4,176,153 and 4,178,976, all listed above, disclose apparatus wherein the inner tube from which liquid is discharged also contains a third tube through which the blow molding gas is discharged. In these apparatus, the blow molding gas is subsequently vented from the container through an annular flow passageway defined between the inner filling tube and the outer mandrel tube.
Also, U.S. Pat. No. 3,251,915 shows a fixed filling assembly that is integral with the extruder head and that utilizes a fixed amount of gas trapped in the head space of a liquid product supply vessel to dispense the liquid product to a container to be filled. However, such an arrangement does not maintain a substantially constant pressure head above the product to be dispensed inasmuch as the pressure head necessarily decreases as the head space in the supply vessel increases during dispensing of the product.
Apparatus operating generally in accordance with the teachings of the above-listed U.S. Pat. Nos. 3,523,401 and Re. 27,155 is sold commercially by Automatic Liquid Packaging, Inc., 2445 East Oakton Street, Arlington Heights, Ill. 60005, U.S.A.
Although the commercial apparatus discussed above works very well with many applications, it would be desirable to provide method and apparatus whereby the filling time of the molded container could be reduced.
Further, it would be desirable to provide a filling apparatus in which the valve mechanism controlling the discharge of the liquid product has a highly effective and a drip-free shut-off capability. It has been found that, in some instances, a small drop of liquid product may cling to the filling apparatus after it is withdrawn from the molded and filled container. Subsequently, when the filling apparatus is next extended into a new length of parison, the discharge of pressurized gas into the parison (during the molding step) will carry with it the drop of liquid product. The drop of liquid product may or may not be broken into a number of smaller drops by the pressurized gas stream. In any case, the single drop, or the resulting smaller drops, may impinge upon the walls of the container being formed from the hot, soft parison with the pressurized air. This can cause undesirable cratering or pitting of the soft interior surface of the blow molded container. Thus, it would be desirable to provide a valve mechanism in which tight, drip free, shut-off can be ensured.
In addition, it would be advantageous to provide a method and apparatus for supplying the liquid product to the filling apparatus at a desired pressure. Devices have been proposed for filling a container, such as one blow molded from thermoplastic material, wherein the liquid product is discharged to a filling nozzle by means of piston and cylinder actuators. See, for example, U.S. Pat. No. 3,670,787. However, there are advantages with a system that does not require the use of one or more hydraulic piston and cylinder actuators for supplying the desired volume of liquid product at the desired pressure to the blow molding and filling assembly.
Further, it would be beneficial to provide a means in such a system for determining the amount of liquid product available for supplying to the molding and filling assembly, and to provide means for automatically replenishing the supply as the liquid product is discharged from the molding and filling assembly.
In addition, with such a system, it would be desirable to provide the capability for steam sterilization of the system prior to the introduction therein of a sterile liquid product. Such a system should facilitate the use of a sterile liquid in accordance with procedures that comply with conventional requirements applicable to the handling of sterile liquids.